The present invention relates to a battery with a spacer member mounted between an electrode group and a cover to prevent the slippage out of position of the electrode group inside a case.
A battery needs a structure preventing the slippage out of position of the electrode group mounted inside the case, because if the electrode group inside the case slips, the cover tab fixed on the inner face of the cover enters into contact with the positive and negative electrode groups resulting in an internal short circuit. As a structure for avoiding this inconvenience, the open side of the case is set, the internal diameter is narrower and a cylindrical spacer structure is adopted between the electrode group and the cover. It is impossible to proceed by setting one part of the case for all batteries. For example, it is impossible to set the corner of the case for a prismatic type battery.
In the batteries with a case unable to be set, a spacer is placed between the electrode group and the cover. FIG. 1 is a section view showing a battery mounted with a spacer. In this battery, to prevent the slippage out of position towards the top of the electrode group 2, spacer 7 is placed at the open side of the case 1. As shown in the perspective view Of FIG. 2, the spacer 7 made of plastic is cylindrical so as to fit the inner face of the case. The cylindrical spacer 7 holds the electrode group down by its outer part, preventing it from going up.
Further, in the battery shown in FIG. 1, as shown in FIG. 3, a cover tab 5 made of a metal plate, inside the internal face of the cover 4, is fixed and insulated from the cover 4. The cover tab 5 is electrically connected to the battery electrode 9 that projects out of the upper face of the cover 4. Both the battery electrode 9 and cover tab 5 are insulated and fixed to the cover 4. To insulate the battery electrode 9, a gasket 10 has been inserted between the battery electrode 9 and the cover 4. To insulate the cover tab 5, a plastic insulator 8 has been interposed between the cover tab 5 and the cover 4.
As shown in FIG. 1., the cover tab 5 is connected at one end of a connecting tab 6 made from a thin metallic plate cut like a tape and at the other end of this connecting tab 6 is connected an electrode tab 3. The connecting tab 6, is bent at a right angle to facilitate the electric welding of the cover tab 5 and an electrode tab 3 at each end. One of the bent parts is electrically welded to the electrode tab 3 and the other to the cover tab 5. Further, to prevent the connecting tab 6 from lowering, a support 11 has been designed to connect the opposite sides of the spacer 7 and forms one unit with it. The connecting tab 6 is placed on top of the support 11. If there is no support 11 in the spacer 7, it becomes impossible to prevent the lowering of the long connecting tab 6. It is possible to shorten the connecting tab to prevent lowering, but it will be impossible to connect a short connecting tab to the cover tab. When connecting the connecting tab to the cover tab, the bent part of the connecting tab is lifted from the spacer and then connected. After having lifted the connecting tab from the spacer, and having connected it to the cover tab, the connection of the cover to the top of the spacer will cause the long connecting tab to assume a corrugated shape. For that reason, the connecting tab is lowered and the contact with the electrode group is made easier. The role of the support of the spacer is to prevent this inconvenience. When the cover is fixed to the spacer, the connecting tab becomes straight and because it cannot stick out of the upper part of the spacer, it cannot be connected to the cover tab.
The battery shown in FIG. 1 is manufactured as described hereunder through the process shown in full line in FIG. 4.
(1) Weld by electric welding one of the bent parts 6A of the connecting tab 6 to the electrode tab 3 of the electrode group 2, before inserting the electrode group in the case 1. When welding, hold the connecting tab 6 and the electrode tab 3 together from both sides using a welding electrode and, in this condition, send a strong electric current into the electrode tab 3 and the connecting tab 6. The strong electric current will weld by thermal welding the contact faces of the connecting tab 6 and the electrode tab 3.
(2) Place the cylindrical spacer 7 on top of the electrode group 2. Place on top of the support 11 built in the spacer 7, one side of the connecting tab 6 connected to the electrode tab 3. To connect the connecting tab 6 to the cover tab 5, pull up the other end of the connecting tab 6 from the spacer 7.
(3) Prepare the cover 4, fixed in an insulated condition with the cover tab 5 and the battery electrode 9, to be electrically connected. The structure of this cover 4 is manufactured by another process.
(4) Electric weld the other bent part 6A of the connecting tab 6 that sticks out from the spacer 7, to the cover tab 5 of the cover 4. At that moment too, hold together from both sides with the welding electrode the connecting tab 6 and the cover tab 5, and heat the same by running a strong current therethrough to perform the welding.
(5) Place together into the case 1, the electrode group 2, the spacer 7 and the cover 4.
(6) Fix to the open side of the case 1, the circumference of the cover 4 by laser welding. Through that process, the open side of the case 1 is sealed by the cover 4.
In the process shown in full line in FIG. 4, after having connected the connecting tab 6 to the cover tab 5, the electrode group 2 can be inserted into the case 1. In this method, as shown by the dotted line in FIG. 4, make sure to insert the electrode group 2 already connected to the connecting tab 6 into the case 1, then introduce the spacer 7 into the case 1 and it becomes possible to electrically weld the connecting tab 6 to the cover tab 5. As for the process shown by the dotted line, to be able to connect the connecting tab 6 to the cover tab 5, it is necessary to lift one end of the connecting tab 6 out of the spacer 7.
Because the prior art batteries shown in FIG. 1 used to be manufactured as mentioned above, it was difficult to insure good productivity in mass production. In particular, because the electric welding was performed while lifting one end of the connecting tab out of the spacer, the process of connecting the connecting tab to the cover tab takes much time. The spacer is placed between the electrode group and the cover and then, because the insulation panel is fixed between the cover tab and the cover, there are numerous processes for assembling the spacer to the insulation. Further, because it is necessary to connect the electrode group through a long connecting tab to the cover tab, the weak point is that the connecting tab used to come off easily due to shock or dropping.
The present invention has been developed to solve the problems described above. The most important object of the present invention is to achieve mass production of batteries at high productivity and low cost by reducing the number of parts.
Furthermore, another important object of the present invention is to reduce the percentage of defective products resulting from the production process and to produce batteries with superior antishock characteristics.
The above and further objects and features of the invention will more fully be apparent from the following detailed description and accompanying drawings.